1. Field of the Invention
The present invention relates to a frequency-sensitive shock absorber, and more particularly, to a frequency-sensitive shock absorber configured to satisfy both a ride comfort and a steering stability, minimize a rise in costs, and make it advantageous to design basic components by controlling damping forces with respect to a small amplitude and a large amplitude during a compression stroke and a rebound stroke of a piston valve.
2. Description of the Related Art
Generally, suspension systems are installed in vehicles so as to improve a ride comfort by absorbing and damping a vibration or shock which is transferred from a road surface to an axle during driving. As one of such suspension systems, a shock absorber is used.
The shock absorber operates with a vibration of a vehicle according to a condition of a road surface. At this time, a damping force generated by the shock absorber is varied according to an operating speed of the shock absorber, that is, a high or low operating speed of the shock absorber.
A ride comfort and a driving stability of a vehicle may be controlled according to how to adjust a damping force characteristic generated by the shock absorber. Therefore, in designing the vehicle, it is very important to adjust the damping force characteristic of the shock absorber.
A conventional piston valve is designed to have a constant damping characteristic at a high speed, a medium speed, and a low speed. Therefore, when intending to improve a ride comfort by reducing a low-speed damping force, a medium- or high-speed damping force may also be influenced. In addition, a conventional shock absorber has a configuration in which a damping force is varied according to a change in a speed of a piston, regardless of a frequency or a stroke. In the case of the damping force varied according to only the change in the speed of the piston, the same damping force is generated in various road conditions. Consequently, it is difficult to satisfy both the ride comfort and the steering stability.
Therefore, there is a need for continuous research and development for a valve structure of a shock absorber, which is capable of varying a damping force according to various road conditions, that is, a forcing frequency and a stroke, to thereby satisfy both the ride comfort and the steering stability.
There is also a need for a valve structure of a shock absorber, which is advantageous to mass production and fabrication automation and is capable of implementing performance desired by a designer in a structure for opening or closing a passage so as to vary a damping force and reducing the number of parts by simplifying the structure, thereby reducing manufacturing costs.